1. Field of the Invention
This invention relates to a novel surfactant water flooding enhanced oil recovery process. This invention also relates to a glyceryl ether sulfonate composition of matter. The invention further relates to fluids containing a glyceryl ether sulfonate. The solutions are useful for recovering petroleum in enhanced oil recovery processes.
2. Prior Art
The sequence for recovering petroleum from subterranean petroleum deposits ordinarily comprises a first phase, referred to as primary recovery, in which petroleum is recovered by pumping or permitting the petroleum to flow to the surface of the earth through wells penetrating and in fluid communication with the formation. Once this phase is completed, a secondary production phase is frequently applied. In the secondary phase, water is injected into the formation via an injection well in fluid communication, which displaces petroleum through the formation to another, remotely located well from which petroleum and water flow to the surface of the earth. While waterflooding recovers an additional quantity of oil economically, water does not displace petroleum efficiently, since water and oil are immiscible and the interfacial tension between water and oil is quite high. Accordingly, as much as 70 percent of the oil originally present in the formation is commonly left even after completion of waterflooding operations.
Surfactant waterflooding is a tertiary phase method employed after water flooding recovery is exhausted. The use of surfactant waterflooding has been discussed in many prior art references, and numerous field trials have been undertaken employing surfactant containing fluids. Petroleum sulfonates and other simple organic sulfonate anionic surfactants may be employed in very low salinity formations, but many petroleum formations contain water whose salinity exceeds the level in which petroleum sulfonates may be employed advantageously.
Prior art references suggest the use of surfactants which are both ethoxylated and sulfated or ethoxylated and sulfonated in high salinity environments. Numerous references suggest the injection of a complex mixture of simple anionic surfactants such as petroleum sulfonate and water soluble surfactants such as ethoxylated and sulfated or ethoxylated and sulfonated surfactants. While laboratory tests indicate such complex mixtures effectively displace petroleum in the presence of high salinity water, field application has frequently been disappointing for a number of reasons. One reason for failure of the multi-surfactant containing fluids is related to the different rates of adsorption of the dissimilar surfactants from the aqueous fluid as the fluid passes through the subterranean earth formation. Since optimum performance of a multi-component surfactant system is achieved only when the various surfactant species are present in a critical ratio, differential adsorption necessarily changes the ratio of the surfactants and therefore renders the fluid less effective or completely ineffective for low surface tension displacement of petroleum. The use of essentially single surfactant fluids, in which the surfactant is an ethoxylated and sulfated or ethoxylated and sulfonated surfactant is also suggested in the prior art, but it has heretofore been difficult to compound a fluid containing substantially only one surfactant which is effective under high salinity conditions for recovering oil from subterranean formations.
In view of the serious current shortage of petroleum and shortcomings of the prior art techniques, it can be appreciated that there is a significant need for a surfactant waterflooding oil recovery method employing a fluid containing essentially a single surfactant species which efficiently displaces oil from subterranean formations.
U.S. Pat. Nos. 4,066,124; 4,077,471 and 4,299,711 describe surfactants useful in secondary recovery processes. Surfactants disclosed in these U.S. patents all have hydroxypropyl groups attached to the sulfonate moiety and do not demonstrate the phase modifying characteristics and chemical compatibility of the present invention. U.S. Pat. No. 4,288,334 discloses a surfactant which contains multiple hydroxypropyl groups but no sulfonate moiety and which is not effective in an enhanced oil recovery process when used by itself.